Del Mar Photonics - Newsletter Fall 2010 - Newsletter Winter 2010

Spectroscopy and Ultrafast Dynamics of Nanotubes

Del Mar Photonics customers present their research at the

NT10 Eleventh International Conference on the Science and Application of Nanotubes

Surfactant and structure-dependent exciton mobility in SWCNTs
Anni Siitonen, University Of Jyväskylä, Finland| Dmitri Tsyboulski, Rice
University, Houston TX, USA| Sergei Bachilo, Rice University, Houston
TX, USA| Bruce Weisman, Rice University, Houston TX, USA

Exciton mobility in nanotubes is an intriguing phenomenon that plays a central role in nonlinear optical responses of single-walled
carbon nanotubes (SWCNT) and results in the strong quenching sensitivity of SWCNT photoluminescence (PL) to covalent functionalization or oxidation. It was previously shown that singlemolecule reactions of diazonium salts with individual SWCNTs can be observed as stepwise quenching of PL intensity. By analyzing the relative amplitudes of quenching steps, the range of exciton excursion along the nanotube during their lifetime was found be ~100 nm. In this study we describe a re ned experimental methodology for quantifying exciton mobility of individual SWCNTs. We report exciton ranges of 140-240 nm in different environments that correlate weakly with PL intensity. These results are consistent with a model of localized SWCNT excitons having substantial mobility along the nanotube axis. An approximate proportionality was deduced between exciton range and the square root of excitonic lifetime indicating that exciton motion is diffusional and that it depends systematically on environment. However, exciton ranges measured for a variety of (n,m) structures indicate no substantial dependency on chirality, diameter and PL intensity.

Del Mar Photonics featured customer Bruce Weisman. Professor Weisman ordered Trestles Ti:Sapphire laser with built-in DPSS pump laser.

Professor Weisman wrote: Our applications are for carbon nanotube excitation, mostly with a cw beam but in some experiments with mode-locked pulses.

Del Mar Photonics offered Trestles Ti:Sapphire model with both CW and femtosecond modes of operation. Detailed laser specifications are as follows (request a quote):

Trestles Ti:Sapphire laser with built-in DPSS pump laser

Ti:Sapphire oscillator having a tuning range of 710-920 nm;
Output power: 30mW (@3W pump, in the whole range);
Spatial mode: TEMoo;
Polarization: linear horizontal;
Repetition rate: 80 MHz;
Pulse duration: <100 fs
Electronic starter with TTL output for mode-locked mode
observation. Output mirrors included.
USB-controlled tuning slit for wavelength tuning

3BRF-TM 3-plate BRF for CW lasers (step motor controlled tuning)
Provides CW tuning and 40 GHz linewidth of the Trestles fs
lasers in CW mode; output power @700 nm - >50 mW (3W pump)

3 W pump DPSS laser with control and power supply unit
Power: 3 W
Wavelength: 532 nm
Beam size: 2.0 mm
Spatial mode: TEM00
Bandwidth: 30 GHz
Divergence: 0.4 mrad
M squared: < 1.1
Power stability: < 0.4 % RMS
Noise: < 0.4% RMS
Noise bandwidth: 1 Hz - 6 MHz
Pointing stability: < 2 microrads/C
Polarization ratio: 100:1
Polarization direction: horizontal
Coherence length: < 1 cm
Beam angle: < 1 mrad
Umbilical length: 1.5 m
Warm-up time: 10 min

Trestles CW/fs laser for carbon nanotubes spectroscopy and photophysics research at Rice University

Single nanotube experiment with tunable Ti:Sapphire laser Trestles Finesse

R. Bruce Weisman Professor of Chemistry

Research Statement
Dr. R. Bruce Weisman and his group investigate the spectroscopy and photophysics of fullerenes and carbon nanotubes. All of these are closed nanoscopic structures formed from carbon atoms. Fullerenes, such as C60, C70, and their chemical derivatives, have unusual molecular properties that cause interesting behaviors following the absorption of light. Time-resolved absorption and emission methods are used to study radiationless decay, photochemical reactions, and energy transfer in fullerenes. Another major research topic is single-walled carbon nanotube spectroscopy. Following the discovery in Weisman?s lab of near-infrared nanotube fluorescence, the group has measured and unraveled the absorption and emission spectra of more than 30 semiconducting nanotube species. Follow-up projects include detailed elucidation of nanotube electronic structure, as well as applications in non-invasive biomedical imaging and analytical nanotechnology.

 

Other presentation in spectroscopy and ultrafast dynamics of nanotubes

Femtosecond four-wave-mixing spectroscopy of freely suspended and fully characterized single-wall carbon nanotubes

Pasi Myllyperkiö, Nanoscience Center, University of Jyväskylä, Finland| Olli Herranen, Nanoscience Center, University of Jyväskylä, Finland| Jyri Rintala, Nanoscience Center, University of Jyväskylä, Finland| Hua Jiang, Center for New Materials, Aalto University, Finland| Andreas Johansson, Nanoscience Center, University of Jyväskylä, Finland| Prasantha R. Mudimela, Center for New Materials, Aalto University, Finland| Zhen Zhu, Center for New Materials, Aalto University, Finland| Albert G. Nasibulin, Center for New Materials, Aalto University, Finland| Esko I. Kauppinen, Center for New Materials, Aalto University, Finland | Markus E. Ahlskog, Nanoscience Center, University of Jyväskylä, Finland | Mika Pettersson, Nanoscience Center, University of Jyväskylä, Finland

We have characterized the individual properties of freely suspended single-wall carbon nanotubes, using both Raman spectroscopy and electron diffraction measurements in a transmission electron microscope. The two techniques give mutually independent routes to determine the chirality of the nanotube [1,2], which allows us to nd the corresponding detailed band structure. With help of that knowledge we set up time-resolved (femtosecond) four-wave-mixing (FWM) measurements and show that it is possible to obtain fs-FWM signals from individual suspended semiconducting single-wall carbon nanotubes. These measurements are the rst in the femtosecond regime and they open interesting perspectives for measurements of ultrafast dynamics and nonlinear optical response from individual nanotubes. Within this study we next intend to measure directly the vibrational coherence in nanotubes of known chirality.

 [1] J. Rintala et al., J. Phys. Chem. C 113 (2009) 15398. [2] H. Jiang et al., Carbon 45 (2007) 662.

Observation of coherent excitation of the interlayer shearing mode in multilayer graphene

Leandro Malard, Department of Physics, Columbia University, USA | Davide Boschetto, Department of Physics, Columbia University, USA| Chun Hung Lui, Department of Physics, Columbia University, USA| Z. Q. Li, Department of Physics, Columbia University, USA| Kin Fai Mak, Department of Physics, Columbia University, USA| Tony F. Heinz, Department of Physics, Columbia University, USA

Raman spectroscopy is one of the key methods for the characterization of single and multilayer graphene. In the bulk limit, the lateral motion of adjacent graphene planes gives rise to a Raman active low-frequency mode, the so-called interlayer shearing mode. Coherent excitation of this mode has been observed by femtosecond time-resolved re ectivity [1]. For the case of few-layer graphene, related modes are predicted to be present and to exhibit different properties as a function of layer thickness [2]. Here we report the observation of coherent oscillation of such shearing mode phonons in multilayer graphene. The experiments are performed on mechanically exfoliated graphene samples using femtosecond laser excitation pulses and time-delayed femtosecond probe pulses in a transient re ectivity measurement. We will discuss the characteristics of shearing mode phonons as a function of the thickness of multilayer graphene. The coherent shearing-mode phonons in graphite exhibit a period of 800 fs, with a damping time of around 10 ps. Reducing the number of layers, we observe a red shift in the frequency of the mode, whereas its damping rate remains unchanged. The experimental frequency shifts with sample thickness can be explained surprisingly accurately using zone folding of the graphite phonon dispersion relation.

 [1] T. Mishina et al., Phys. Rev. B 62, 2908 (2000) [2] S. K. Saha et al., Phys Rev. B 78, 165421 (2008)

Ultrafast photoluminescence from graphene

Chun Hung Lui, Columbia University, USA| Kin Fai Mak, Columbia University, USA| Jie Shan, Case Western Reserve University, USA| Tony F. Heinz, Columbia University, USA Since graphene has no band gap, light emission is not expected from fully relaxed carriers. However, we observed strong light emission from monolayer graphene under excitation by ultrashort (30-fs) laser pulses. The emission spectrum was found to extend from the visible range to photon energy of 3.5 eV in the near UV, greatly exceeding that of the pump laser at 1.5 eV. Beside detailed measurements of the emission spectra for different pump uences, we have also applied an ultrafast time-domain correlation technique in which light emission was measured as a function ofthe temporal separation between a pair of femtosecond excitation pulses. A dominant relaxation time of a few tens of femtoseconds was observed. Our results indicate that the unusual light emission process originates from non-equilibrium photoexcited charge carriers in graphene. Further analysis reveals strong carrier-carrier scattering processes and rapid electronic cooling through optical phonon emission in graphene on the sub-100fs time scale. Observation of Coherent Lattice Vibrations in Metallic Single-Walled Carbon Nanotubes Kenji Yamamoto, Graduate School of Information Science and Technology, Hokkaido University| Gary.T. Noe, Department of Electrical and Computer Engineering, Rice University| Erik.H. Haroz, Department of Electrical and Computer Engineering, Rice University| Ji-Hee Kim, Department of Physics, Chungnam National University, KOREA| Ki-Ju Yee, Department of Physics, Chungnam National University, KOREA| Yong-Sik Lim, Department of Applied Physics, Konkuk University, Korea| Stephen. K. Doorn, Center for Integrated Nanotechnologies, Los Alamos National Laboratory| Junichiro Kono, Department of Electrical and Computer Engineering, Rice University| Kazuhisa Sueoka, Graduate School of Information Science and Technology, Hokkaido University We performed degenerate pump-probe measurements using a femtosecond Ti:Sapphire source on single-walled carbon nanotubes, synthesized by the arc-discharge method (diameter 1.4-1.7 nm) and suspended in aqueous surfactant. Examination of the probe beam transmittance through the sample reveals the presence of strong, photon-energy-dependent, time-domain oscillations which when Fourier-transformed can be assigned to the generation of coherent lattice vibrations of the radial breathing mode and G-mode phonons in metallic carbon nanotubes. This constitutes the rst observation of coherent lattice vibrations in metallic nanotubes and these results are compared to previous coherent phonon results on smaller-diameter, semiconducting nanotubes and cw resonant Raman data on same-size metallic nanotubes.

Ultrafast carbon nanotubes optical properties for high-bit-rate telecommunications applications

Maud Gicquel-Guezo, FOTON, INSA (Rennes, France) H. Nong, FOTON, INSA (Rennes, France)| M. Perrin, FOTON, INSA (Rennes, France)| C. Levallois, FOTON, INSA (Rennes, France)| F. Grillot, FOTON, INSA (Rennes, France)| S. Loualiche, FOTON, INSA (Rennes, France)| L. Bramerie, FOTON, ENSSAT ,France| A. Maalouff, FOTON, ENSSAT ,France| D. Bosc, FOTON, ENSSAT ,France| J.-C. Simon, FOTON, ENSSAT ,France| R. Fleurier, LEM (Châtillon, France)| B. L. Liang, Electrical Engineering Department (Los Angeles, USA)| D.L. Huffaker, Electrical Engineering Department (Los Angeles, USA)

The quality of information transmission in telecommunications networks requires all-optical-regeneration of the optical signal, as it is damaged through its propagation in long-haul optical bers. Our work focuses on designing ef cient all-optical switches based on ultrafast and nonlinear optical properties of nanomaterials. We highlight here nonlinear optical properties of bundled carbon nanotubes (CNT), in direct comparison with quantum wells (QW): bundled CNT present ultrafast absorption dynamics and large 1D-excitonic nonlinearities. We aim at demonstrating the huge potential of bundled CNT-based optical devices for telecom applications[1], as simple-process and low-cost solution in comparison with QW-based devices [2]. Intrinsic properties of luminescent CNT are intensively investigated by international scienti c community. Our study focuses more on CNT in bundles, where extrinsic properties govern optical properties. Thus, we preliminarily present linear optical properties of bundled CNT- lms, in comparison with individualized luminescent CNT- lms. Redshift and broadening of CNT optical transitions are clearly observed, from individualized to bundled CNT. Linear absorption in telecom window is also enhanced and we suggest the ability of bundled CNT-based devices to regenerate wavelength division multiplexing channels. Finally, nonlinear optical properties of bundled CNT- lms are investigated using a femtosecond-pulses pump-probe experiment at 1550 nm. We compare the recorded dynamics of bundled CNT- lms with QW. The subpicosecond recovery time of CNT-based devices should be suitable for a rate of telecom signal as high as 500 Gb/s. [1] H. Nong et al., Appl. Phys. Lett. (2010). [2] M. Gicquel- Guézo et al., Appl. Phys. Lett 85, 5926 (2004).

Energy transfer dynamics in functionnalized carbon nanotubes.

Damien Garrot, Laboratoire de Photonique Quantique et moléculaire, Ecole Normale Supérieure de Cachan, France|
Cyrielle Roquelet, Laboratoire de Photonique Quantique et
moléculaire, Ecole Normale Supérieure de Cachan, France|
Christophe Voisin, École Normale Supérieure, Laboratoire
Pierre Aigrain, France| Jean Sébastien Lauret, Laboratoire de
Photonique Quantique et Moléculaire, CNRS - Ecole Normale
Supérieure de Cachan, France| Valérie Alain-Rizzo, Laboratoire
de Photophysique et Photochimie Supramoléculaires et
Macromoléculaires, École Normale Supérieure de Cachan, France

Functionnalized NT are very promising materials for light harvesting applications since they combine the exceptional transport properties of carbon nanotubes and the versatility of organic dyes. In this study we show that a very strong interaction can be induced between porphyrin molecules and nanotubes, even in the context of non-covalent functionnalization. This interaction leads to very ef cient energy transfer from the dye to the nanotube [1, 2]. We investigate its dynamics by means of broadband femtosecond transient spectroscopy. We show that the excitation of the porphyrin molecule is rst followed by a internal energy conversion down to the Q band (~100fs), followed by a subpicosecond transfer to the nanotube. The population build up is observed on the lowest exciton level of the nanotube in agreement with photoluminescence measurements. Finally, we show that the quantum ef ciency of this transfer can be very close to 1 with an almost total quenching of the porphyrin luminescence but a strong luminescence of the nanotube and with a strong acceleration of the relaxation in the donor. [1] G.Magadur et al ChemPhysChem 9, 1250 (2008) [2] C.Roquelet et al, http://arxiv.org/abs/0910.5619v1

Ultrafast energy transfer at a single-walled carbon nanotubepolymer molecular junction
 

Samuel Stranks, University Of Oxford| Christian Weisspfennig,
University Of Oxford| Patrick Parkinson, University Of Oxford|
Michael Johnston, University Of Oxford| Laura Herz, University Of
Oxford| Robin Nicholas, University Of Oxford

We report an ultrafast energy transfer process between a singlewalled carbon nanotube (SWNT) and a dispersing semi-conducting polymer, poly(3-hexylthiophene) (P3HT), three orders-of-magnitude faster than reported previously for other SWNT-polymer systems. This composite is a promising candidate for use in organic photovoltaics (OPVs). However, despite reports that there can be a type-II heterojunction alignment between the two materials, OPV devices to date have shown poor performances. In this work, we study puri ed P3HT-SWNT nanohybrid structures. We use photoluminescence measurements to observe the quenched polymer emission and subsequent nanotube emission following energy transfer. Femtosecond up-conversion spectroscropy is used to monitor the quenched time-decay of the polymer emission and transient absorption studies are used to probe for charge on the P3HT resulting from charge separation processes. The photoluminescence measurements show that ef cient energy transfer occurs from excitation of the wrapping P3HT polymer to the SWNTs and this transfer occurs on a 430 fs time scale. The transient absorption studies demonstrate a signi cant initial charge generation but that this decays away rapidly. We conclude that the energy transfer process occurring between the P3HT polymer and SWNT dominates over the short-lived charge transfer and this explains the poor OPV ef ciencies observed to date. The energy transfer is an ultrafast process due to intimate wrapping of the polymer around the SWNT leading to Förster-type resonant energy transfer. Our results show that the development of SWNT-based OPVs require use of smaller-diameter tubes, alternative polymers, or an altered geometry, all with the aim to facilitate longer-lived charge separation. Friday,

Exciton-Plasmon Coupling and biexcitonic nonlinearrities in individual carbon nanotubes
 

Igor Bondarev, North Carolina Central University| Lilia Woods,
University of South Florida| Kevin Tatur, University of South Florida
 

We study theoretically the interactions of excitonic states with surface electromagnetic modes of small-diameter (~1nm) semiconducting single-walled carbon nanotubes (CNs). We show that these interactions can result in strong excitoninterband- surface-plasmon coupling in individual CNs[1]. The quantum con ned Stark effect with an electrostatic eld applied perpendicular to the CN axis can control the exciton-plasmon coupling strength, and exciton emission accordingly[2]. We further extend our studies to analyze the interactions of biexcitons (observed recently in single-walled CNs by the femtosecond transient absorption spectroscopy technique[3]) with the interbandsurface- plasmon modes. We show the biexciton-plasmon coupling tunability by means of the quantum con ned Stark effect, both for the ground-ground state and for the ground-excited state biexcitonic con gurations. We expect our results to open up paths to new tunable optoelectronic device applications of small-diameter semiconducting CNs, including the strongexcitation regime with optical non-linearities. Supported by NSF (HRD-0833184), NASA (NNX09AV07A), and ARO (57969-PH-H). [1] I.V.Bondarev, K.Tatur, and L.M.Woods, Optics Commun. 282,661 (2009). [2]I.V.Bondarev, L.M.Woods, and K.Tatur, Phys. Rev. B 80,085407(2009). [3]D.J.Styers-Barnett, S.Pellison, B.P.Mehl, et al., J.Phys. Chem. C 112,4507(2008).
 

Importance of Exciton Coupling on the Upper Density Limit of Optically Created Excitons in SWCNTs
 

Mitchell Anderson, Department of Physics, Engineering Physics
& Astronomy, Queen’s University| Yee-fang Xiao, Department of
Physics, Engineering Physics & Astronomy, Queen’s University| James
Fraser, Department of Physics, Engineering Physics & Astronomy,
Queen’s University
An important feature of single walled carbon nanotubes (SWCNTs) are their quasi 1-D, chiral structure which gives rise to exitonic photoluminescence from 2/3 of the species. These excitons can be created in a number of ways including electrically and optically. Future uses and technologies involving CNTs as optical emitters require an understanding of the excitonic structure and dynamics within the CNT. The excitonic structure is being extensively studied and recently an upper density limit for photo-excited excitons has been observed that is surprisingly low. This upper density limit has been explained as a diffusion limited exciton-exciton annihilation process with a diffusion length of 90 nm when observed in sodium cholate coated SWCNT in ensemble samples suspended in D2O [1]. In contrast, saturation occurs at pump uences an order of magnitude smaller in long single air-suspended SWCNTs [(9,8), (10,8)] [2]. In Monte Carlo simulations of exciton dynamics which include dipole-dipole interactions, the excitons exhibit an attractive bias which results in an increased interaction length inversely proportional to the dielectric environment and effective mass. Experimentally the dipole interaction energy is consistent with our observation of a density dependant blue shift of emission observable only at short time delays. This is observed by a novel variant of femtosecond excitation correlation spectroscopy.

[1] Murakami, Y. and Kono, J. Phys. Rev. Lett. 102, 037401 (2009) [2] Xiao, Y.-F. et al., Phys. Rev. Lett. 104, 017401 (2010).

full program

Del Mar Photonics - Newsletter Fall 2010 - Newsletter Winter 2010

Del Mar Photonics is involved in research of CNTs, graphene nanoplatelets and graphene materials, develops advanced multifunctional materials for variety of applications as well as research instrumentation for characterization of the above.

We currently we can offer:

1) Graphene nanoplatelets: the stack of multi-layer graphene sheets with high aspect ratio, diameter: 0.5-20 µm, thickness: 5-25 nm.
2) Graphene materials: Graphene Powder, Graphene Oxide Powder, Graphene Suspension.
3) Carbon Nanotubes.
 

Contact our application team to discuss your requirements for high-performance nanocomposite materials, display materials, sensing materials, ultracapacitors, batteries, energy storage and other area to improve electrical, thermal, barrier, or mechanical properties by using low-cost nano-additive.

Graphene nanoplatelets are the stack of multi-layer graphene sheets including platelet morphology, with characteristics as follows:

Request a quote for graphene nanoplatelets

Applications:

The high performance composite additives in PPO, POM, PPS, PC, ABS, PP, PE, PS, Nylon and rubbers.
To improve composite tensile strength, stiffness, corrosion resistance, abrasion resistance and anti-static and lubricant properties.
Mechanical properties modifications.
Conductivity modification.
Fuel tank coating.
In electronic enclosures add electrical conductivity to polymers at low densities of 3 to 5 wt%.
Adding EMI or RFI shielding capabilities to a variety of polymers.
Automotive parts: a composite with nanoplatelets can be painted electrostatically, thereby saving costs.
Aerospace: graphite has long been used in aerospace composites. Nanoplatelets can be combined with other additives to reinforce stiffness, add electrical conductivity, EMI shielding, etc.
Appliances: fortified polymers provide superior thermal and electrical conductivity, thereby saving the costs of separate heat dissipation mechanisms.
Sporting goods: graphite-based composites are stronger and stiffer and lighter than comparable materials.
Coatings and paints: graphene nanoplatelets can be dispersed in a wide variety of materials to add electrical conductivity and surface durability.
Batteries: graphene nanoplatelets increase the effectiveness of Lithium-ion batteries when used to formulate electrodes.
Fuel cells: both bi-polar plate and electrode efficiencies can be improved.

Del Mar Photonics develops advanced instrumentation for research of CNTs, graphene nanoplatelets and graphene materials including lasers for broadband spectroscopy, femtosecond transient absorption and fluorescence measurements.

T&D Scan high resolution Laser Spectrometer based on broadly tunable CW laser
CW single-frequency ring Dye laser
Beacon Femtosecond Optically Gated Fluorescence Kinetic Measurement System
New Hatteras femtosecond transient absorption system
Photon Scanning Tunneling Microscope
 

Graphene is a one-atom-thick planar sheet of sp2-bonded carbon atoms that are densely packed in a honeycomb crystal lattice. The term Graphene was coined as a combination of graphite and the suffix -ene by Hanns-Peter Boehm,[1][2] who described single-layer carbon foils in 1962.[3] Graphene is most easily visualized as an atomic-scale chicken wire made of carbon atoms and their bonds. The crystalline or "flake" form of graphite consists of many graphene sheets stacked together.
The carbon-carbon bond length in graphene is about 0.142 nm. Graphene sheets stack to form graphite with an interplanar spacing of 0.335 nm, which means that a stack of 3 million sheets would be only one millimeter thick. Graphene is the basic structural element of some carbon allotropes including graphite, charcoal, carbon nanotubes, and fullerenes. It can also be considered as an indefinitely large aromatic molecule, the limiting case of the family of flat polycyclic aromatic hydrocarbons. The Nobel Prize in Physics for 2010 was awarded to Andre Geim and Konstantin Novoselov "for groundbreaking experiments regarding the two-dimensional material graphene".[4]

Graphene is a flat monolayer of carbon atoms tightly packed into a two-dimensional (2D) honeycomb lattice, and is a basic building block for graphitic materials of all other dimensionalities. It can be wrapped up into 0D fullerenes, rolled into 1D nanotubes or stacked into 3D graphite.[5]

References

[1] H. P. Boehm, R. Setton, E. Stumpp (1994). "Nomenclature and terminology of graphite intercalation compounds". Pure and Applied Chemistry 66 (9): 1893–1901. doi:10.1351/pac199466091893.
[2] H. C. Schniepp, J.-L. Li, M. J. McAllister, H. Sai, M. Herrera-Alonso, D. H. Adamson, R. K. Prud’homme, R. Car, D. A. Saville, I. A. Aksay (2006). "Functionalized Single Graphene Sheets Derived from Splitting Graphite Oxide". The Journal of Physical Chemistry B 110 (17): 8535–8539. doi:10.1021/jp060936f. PMID 16640401.
[3] H. P. Boehm, A. Clauss, G. O. Fischer, U. Hofmann (1962). "Das Adsorptionsverhalten sehr dünner Kohlenstoffolien". Zeitschrift für anorganische und allgemeine Chemie 316 (3-4): 119–127. doi:10.1002/zaac.19623160303.
[4] Nobel Foundation announcement
[5] Geim, A. K. and Novoselov, K. S. (2007). "The rise of graphene". Nature Materials 6 (3): 183–191. doi:10.1038/nmat1849. PMID 17330084.

Carbon nanotubes (CNTs; also known as buckytubes) are allotropes of carbon with a cylindrical nanostructure. Nanotubes have been constructed with length-to-diameter ratio of up to 132,000,000:1,[1] which is significantly larger than any other material. These cylindrical carbon molecules have novel properties which make them potentially useful in many applications in nanotechnology, electronics, optics, and other fields of materials science, as well as potential uses in architectural fields. They may also have applications in the construction of body armor. They exhibit extraordinary strength and unique electrical properties, and are efficient thermal conductors.
Nanotubes are members of the fullerene structural family, which also includes the spherical buckyballs. The ends of a nanotube may be capped with a hemisphere of the buckyball structure. Their name is derived from their size, since the diameter of a nanotube is on the order of a few nanometers (approximately 1/50,000th of the width of a human hair), while they can be up to 18 centimeters in length (as of 2010).[1] Nanotubes are categorized as single-walled nanotubes (SWNTs) and multi-walled nanotubes (MWNTs).
Chemical bonding in nanotubes is described by applied quantum chemistry, specifically, orbital hybridization. The chemical bonding of nanotubes is composed entirely of sp2 bonds, similar to those of graphite. These bonds, which are stronger than the sp3 bonds found in diamonds, provide nanotubules with their unique strength. Moreover, nanotubes naturally align themselves into "ropes" held together by Van der Waals forces.

[1] Wang, X.; Li, Q.; Xie, J.; Jin, Z.; Wang, J.; Li, Y.; Jiang, K.; Fan, S. (2009). "Fabrication of Ultralong and Electrically Uniform Single-Walled Carbon Nanotubes on Clean Substrates". Nano Letters 9 (9): 3137–3141. doi:10.1021/nl901260b. PMID 19650638.

Del Mar Photonics, Inc.
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